The study, published in the journal Annals of Internal Medicine, showed that Mavacamten reduced left ventricular outflow tract (LVOT) obstruction and improved exercise capacity and symptoms in patients with obstructive hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy is a disease in which the heart muscle (myocardium) becomes abnormally thick (hypertrophied) that makes it make it harder for the heart to pump blood. Most people with hypertrophic cardiomyopathy have a form of the disease in which the wall (septum) between the two bottom chambers of the heart (ventricles) becomes enlarged and restricts blood flow out of the heart (obstructive hypertrophic cardiomyopathy).

The obstructive phenotype of hypertrophic cardiomyopathy (HCM) entails left ventricular hypercontractility with left ventricular outflow tract (LVOT) obstruction and can result in exercise intolerance, exertional dyspnea, chest pain, or fatigue despite management with negative inotropes like β-blockers and nondihydropyridine calcium channel blockers. The non-FDA-approved drug mavacamten is a small molecule that reduces hypercontractility by inhibiting the binding of β-cardiac myosin to actin.

This study demonstrates impressive improvements in LVOT obstruction, symptoms, and exercise tolerance with a drug from a novel therapeutic class in patients with refractory, symptomatic, obstructive HCM.

The study lacks a control group or blinding but sets the stage for a larger placebo-controlled, double-blind, phase 3 study currently recruiting 220 participants and using an endpoint of improvement in symptoms and exercise tolerance (EXPLORER-HCM; NCT03470545). Success could transform therapy for this difficult condition.

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